The full proceedings paper is at: http://www.extension.org/72867 This project was started to work with regional CIG projects to calibrate and harmonize Phosphorus Indices across the U.S., demonstrate their accuracy in identifying the magnitude and extent of phosphorus loss risk, and provide suggestions to refine or improve existing Indices. This research is important to provide consistency among state Phosphorus Indices and their subsequent recommendations.

1. Water to Worth 2015
Advancing Sustainability in Animal Agriculture
Seattle, WA
Refining P Indices
Andrew Sharpley
Crop, Soil,& Environmental Sciences

2. Maryland implements restrictive STP
thresholds for nutrient mgt. & P
applications
1998

3. 1999
Joint US EPA & USDA Initiative requires P
loss assessment prior to applying P
 Site specific assessment using a P index,
 Soil-specific P threshold level, or
 Soil test P recommendations

4. 2009
• Disparity among Indices
 Varied with soils, topography, & state priorities
• Often, not leading to a decline in STP nor
improvement in water quality
 Legacy effects
• Perceived as “farmer friendly”

5. P loss
kg ha-1
AL AR GA MS NC TN TX
0.5 Low Low Low Low Low High Med.
2.7 Med. High High Low Low V. High High
4.0 Low High Med. Low Low V. high High
5.8 Low V. high V. high Low Med. V. high High
10.9 Low V. high V. high Low Med. V. high High
23.7 Low V. high V. high Low High V. high High
Osmond et al., 2012
The P Index was never
meant to be the
solution to P loss
issues!

6. Main recommendations of SERA-17’s review
 All Indices must represent locally relevant P source
& transport factors
 All Indices must have a zero P application category
 All States must show Indices are directionally &
magnitudinally correct
2010

7. 2012
NRCS funds
six CIGs
across U.S.
to assess P
Indices

8. Peter Kleinman & Doug Beegle

9. • Establish 11 benchmark watersheds
 Water quality information
 Land treatment information
• Identify practices of concerns by
physiographic region (4) using expert panels
composed of
 Farmers & farm advisors
 State & local agencies & environmental groups

10. • Panel will
 Evaluate practices that reduce P loss from
agricultural fields
 Assess P indices & recommend changes
• Compare P Indices to water quality data
& water quality modeling data
 Three models will be used: SWAT, APEX,
APLE, & Drainmod

11. Deanna Osmond

12. • Collate water quality & land treatment data
from 21 plot or watershed projects
• Compare P-Index ratings against water
quality data
• Compare water quality models (SWAT, APEX,
APLE, Drainmod) against water quality data
& P Index ratings
• Refine Southern P Indices

13. John Lory

14. • Assess rigor required in calibrating APEX
 Use data from existing runoff studies in region
 Compare “out-of-the-box” versus fully
calibrated model for evaluating Indices
• Use calibrated model to assess & modify P
Indices
• Develop & assess regional P Index for state’s
consideration
• Work with stakeholders throughout project

15. Libby Dayton

16. • Revise OH-PI through use of field-scale,
edge-of-field monitoring data
• Improve assessment of the potential for P
loss from tile drains
• Integrate additional BMPs into OH-PI
• Develop a web-based, easy to use, web-
based GIS tool

17. Anita Thompson & Laura Good

18. • Previous assessment with field runoff data
found WI Index accurate if avg. runoff &
erosion estimates accurate
• Modify Index to quantify avg. runoff from
frozen/thawing soils
• Identify BMPs to minimize P runoff when
animal manure applied to frozen soils

19. November 14th, 2014
Maryland’s Governor O’Malley pushes
forward a P Management Tool
2014

20. January 20th, 2015
Maryland’s newly elected Governor Hogan
repeals revised P Management Tool
2015

21. June 8th, 2015
Agriculture Article, §§8-801—8-806,
Annotated Code of Maryland
Newly revised P Management Tool
2015

22. • Define unacceptable / high Index rating
that preclude P applications
• Synthesize commonalities among regional
projects & integrate different outcomes
• Build a harmonized framework that yields
consistent P-based risk assessment across
the U.S.
• Lessons learnt